OFFSET
1,1
COMMENTS
The odd-indexed terms are the even-indexed powers of 4 (A013709).
REFERENCES
Calvin C. Clawson, The Beauty and Magic of Numbers. New York: Plenum Press (1996): 96.
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
EXAMPLE
a(4) = 16 because 3/4 + 6/16 + 9/64 + 12/256 = 3/4 + 3/8 + 9/64 + 3/64 = 48/64 + 24/64 + 9/64 + 3/64 = 84/64 = 21/16.
MATHEMATICA
Table[Denominator[Sum[3i/4^i, {i, n}]], {n, 40}]
PROG
(Magma) [Denominator(&+[3*i/4^i: i in [1..n]]): n in [1..25]]; // Bruno Berselli, Sep 03 2012
(PARI) vector(100, n, denominator(sum(i=1, n, 3*i/4^i))) \\ Colin Barker, Nov 09 2014
CROSSREFS
KEYWORD
nonn,easy,frac
AUTHOR
Alonso del Arte, Aug 21 2012
STATUS
approved